我们如何更改MySQL表中列的数据类型?
可以借助MySQL的ALTERTABLE命令来完成。考虑表“Student”,其中“RollNo”列的数据类型声明为Integer,可以从以下查询中看到-
mysql> DESCRIBE Student; +--------+-------------+------+-----+---------+-------+ | Field | Type | Null | Key | Default | Extra | +--------+-------------+------+-----+---------+-------+ | Name | varchar(20) | YES | | NULL | | | RollNo | int(11) | YES | | NULL | | | Grade | varchar(50) | YES | | NULL | | +--------+-------------+------+-----+---------+-------+ 3 rows in set (0.06 sec)
现在假设我们想将RollNo的数据类型从Int(11)更改为Varchar(10),以下查询将做到这一点-
mysql> Alter Table student Modify column RollNo Varchar(10); Records: 3 Duplicates: 0 Warnings: 0 mysql> Desc Student; +--------+-------------+------+-----+---------+-------+ | Field | Type | Null | Key | Default | Extra | +--------+-------------+------+-----+---------+-------+ | Name | varchar(20) | YES | | NULL | | | RollNo | varchar(10) | YES | | NULL | | | Grade | varchar(10) | YES | | NULL | | +--------+-------------+------+-----+---------+-------+ 3 rows in set (0.06 sec)
从上面的查询可以看出,RollNo的数据类型已从整数更改为varchar。